The present invention relates to an inkjet printhead chip. More particularly, the present invention relates to an inkjet printhead chip that has drive circuitry for Preheating ink.
Recently, for example, in PCT Application No. PCT/AU98/00550 the present applicant has proposed an inkjet printing device which utilizes micro-electromechanical (MEMS) processing techniques in the construction of a thermal bend actuator type device for the ejection of fluid from a nozzle chamber.
The aforementioned application discloses an actuator which is substantially exposed to an external atmosphere, often adjacent a print media surface. This is likely to lead to substantial operational problems in that the exposed actuator could be damaged by foreign objects or paper dust etc. leading to a malfunction.
According to a first aspect of the invention, there is provided an inkjet printhead chip that comprises
a substrate that incorporates drive circuitry;
a plurality of nozzle arrangements that are positioned on the substrate, each nozzle arrangement comprising:
a nozzle chamber wall and a roof wall positioned on the substrate to define a nozzle chamber, the roof wall defining an ink ejection port in fluid communication with the nozzle chamber;
an ink ejection member that is positioned in the nozzle chamber and is displaceable towards and away from the ink ejection port to eject ink from the ink ejection port; and
an elongate actuator that is fast, at one end, to the substrate to receive an electrical signal from the drive circuitry and fast, at an opposite end, with the ink ejection member, the actuator incorporating a heating circuit that is connected to the drive circuitry layer the heating circuit being positioned and configured so that, on receipt of, and termination of, a suitable electrical drive signal from the drive circuitry layer, the heating circuit serves to generate differential thermal expansion and contraction, respectively, such that the actuator is displaced to drive the ink ejection member towards and away from the ink ejection port, wherein
the drive circuitry is configured to generate a heating signal which is sufficient to heat the actuator, without generating movement, to an extent such that the ink is heated, prior to generating the drive signal.
The drive circuitry may be configured to generate a series of pulses with pulses of a predetermined first duration defining heating signals and a series of pulses of a predetermined second duration defining drive signals.
The printhead chip may include a number of temperature sensors that are connected to a temperature determination unit for detecting ink temperature and an ink ejection drive unit for determining whether or not preheating of the ink is required.
The drive circuitry may be defined by CMOS circuitry positioned in the substrate. The CMOS circuitry may incorporate control logic circuitry for each nozzle arrangement, which is connected to the heating circuit.
Each control logic circuitry may include shift register circuitry for receiving a data input, transfer register circuitry that is connected to the shift register circuitry to generate a transfer enable signal and to latch the data input and to generate a firing phase control signal, and gate circuitry that is connected to the transfer register circuitry to be activated by the control signal to output a heating pulse which is received by the heating circuit.
Each elongate actuator may have a laminated structure of at least two layers, with one of the layers defining the heating circuit.
Each elongate actuator may have three layers in the form of a middle layer of a resiliently flexible, non-electrically conductive material, and a pair of opposite, substantially identical metal layers.
According to a second aspect of the invention, there is provided an inkjet printhead formed on a silicon wafer and including a plurality of nozzle devices, each nozzle device comprising a nozzle chamber and an aperture through which ink from the nozzle chamber is ejected, an actuator for applying pressure to ink within the nozzle chamber to cause ejection of an ink drop through the aperture, and drive circuitry for controlling the actuator, wherein the drive circuitry and the actuator share area of said silicon wafer.
Preferably the actuator and the drive circuitry overlap.
Preferably the actuator overlies the drive circuitry.
Preferably the actuator is external to the nozzle chamber.
Preferably the actuator is a thermal bend actuator.
Preferably the actuator is attached to a paddle which resides within the nozzle chamber.